KLRK1 and neoplasm: These cells release granzyme B and perforins to initiate direct cytotoxicity against targets (Wu et al. 2020; Shin et al. 2020; Carlsten and Jaras 2019), which is facilitated by the recognition of MHC class I-related molecules such as MICA, MICB, and NKG2D ligands (NKG2DLs) on the surfaces of tumor cells (Wu et al. 2020; Topham and Hewitt 2009).